And what if he decides to get off the train a stop early? Will the guard call British Transport Police to drag him back onto the train to finish the journey?You haven't answered the question a few people have asked you: what happens if you decide not to travel at all? Should you be liable for a full price ticket then? After all, you haven't done what you agreed to do.
If not, why not?
What if someone has to get off early because they've fallen ill. Will they refuse them access to the ambulance until they've paid their penalty fare?